Boilers



A. P. SAHA Oct. 18, 1966 BOILERS Filed Dec. 25, 1964 INVENTOR.

AATTO P. SAHA. fi'

ATTORNEY.

United States Patent Filed Dec. 23, 1964, Ser. No. 420,563 3 Claims. (Cl. 122410) This invention relates to a boiler and a method for producing steam and, more particularly, to improved boiler water circulation in a fire tube boiler.

A little used expedient for increasing heat transfer to boiler water is the provision of downcomer baflles for circulating water downwardly along the sides of the boiler shell to improve the circulation of the water upwardly about the fire tubes. This phenomena usually relies on a decreasing density of the rising steam-water mixture about the fire tubes between the downcomers which is less than the density of the water which has separated from the steam and is passing downwardly between the downcomers and the shell to circulate the boiler water.

It has been found that as the boiler water is heated by the lower fire tubes to generate steam, the increasing volume of the mixture of water and steam moving up wardly about the fire tubes results in choking of the mixture, usually upwardly from. about the middle of the boiler. Such choking reduces the circulation of the water and may cause interface steam pockets to form on the fire tubes resulting in scale and corrosion on the tubes and a reduction in heat transfer to the water.

Improved circulation as herein described is generally applicable to boilers, and is particularly desirable when heat transfer from burning fuel to fire tubes of a boiler is increased, thus substantially lessening the required fire tube area to provide adequate heat for converting boiler water to steam, but requiring better heat transfer from the fire tubes to the boiler water for maximum efliciency.

It is a primary object of this invention to provide a new and improved boiler and, more particularly, to provide for better boiler water circulation and heat transfer to boiler water in a fire tube boiler.

Another object is to provide a new and improved boiler in which fire tubes are positioned between downcomers in the boiler shell and the boiler water is deflected between the downcomers and the shell so that the resultant momentum of the boiler water causes the water tocirculate downwardly more rapidly between the downcomers and the shell, thereby improving boiler water circulating about the fire tubes and heat transfer from the first tubes to the boiler water.

Another object is to provide a new and improved method of circulating boiler water in a boiler.

Still another object is to provide a new and improved method of circulating boiler water in a fire tube boiler by deflecting the water about downoomer bafiles within the boiler shell so that the resultant momentum of the water increases its circulation.

These and other objects of the invention will be apparent from the following description and the accompanying drawing in which:

FIGURE 1 is a vertical, longitudinal sectional view of a fire tube boiler taken generally along the line II in FIGURE 2 with parts broken away and illustrating features of the invention; and

FIGURE 2 is an enlarged, vertical, transverse sectional view taken generally along the line II'II in FIGURE 1.

Referring to the drawings, a fire tube boiler includes a generally cylindrical boiler shell 11 with its longitudinal axis 12 horizontally disposed. A generally cylindrical, relatively large diameter main fire tube 13 extends longitudinally 'of the shell 11 and has its longitudinal axis 14 spaced vertically below the axis 12 of the shell.

As illustrated in FIGURE 1, a suitable cyclonic burner assembly 15 is operably positioned at one end of the fire tube 13 for injecting a fuel such as gas or oil into the main fire tube through a nozzle 16 whereupon the fuel unites with a vortex of combustion air from a suitable blower (not shown) and is ignited to form a flame. The air enters the main fire tube 13 through suitable vanes 18 to form the vortex which travels axially through the main fire tube. The resultant flame and flue gas heats the main fi-re tube. At the end of the main fire tube 13 opposite the burner 15, the flue gas passes through a header 19 and into suitable return fire tubes 20 which terminate in a flue gas header 21 at the burner end of the boiler. Suitable spinners, or vortex generators 22 at the entry to the return fire tubes 20', generate vortices in these tubes.

Downcomer baflies are secured, as by axially spaced arms 24, to either side of the shell 11 within the boiler and project above the center of the shell '11 and extend generally the length of the shell and are parallel to and spaced from the adjacent side of the shell so that the sides of the main fire tube 13 and the downcomers 23 diverge from each other in an upward direction. The return fire tubes '20 are positioned about the main fire tube 13 and between the downcomers 23 as illustrated in FIGURE 2 to provide a substantially eflective increasing open area across the boiler in an upward direction. Thus, as boiler water circulates about the fire tubes, the increased open area accommodates the expansion of the resultant mixture of steam and water, and effectively prevents choking of the mixture as the steam moves toward a steam outlet 25 in the top of the boiler shell 11.

As the steam moves to the steam separates from the steam and the downcomers 23 and the shell 11, in part because of the difference in density between the lighter steam-water mixture about the fire tubes and the heavier separated water passing downwardly about the downcomers. However, the circulation of boiler water can be greatly improved by the provision of a deflector baffle 26 higher than the downcomers 23 and extending generally the length of the shell and preferably at the boiler water level, so that as the steam moves about the deflector 26, the Water is given a substantial velocity outwardly in opposite directions toward the opposite sides of the cylindrical shell 11 which are here inclined outwardly and downwardly to cause the water to change direction downwardly between the adjacent d-owncomer and the shell, after it has separated from the steam and be carried downwardly by the resultant momentum.

Circulation of water about the downcomers can be further increased by directing steam condensate through return inlets 27 into the boiler shell 11 alongside the downcomers 23, as shown in FIGURE 2.

While a preferred embodiment of the invention has been described and illustrated, it will be understood that the invention is not limited thereto but may be otherwise embodied within the scope of the following claims.

I claim:

1. A boiler comp-rising a generally cylindrical boiler shell for holding boiler water and steam, said shell having a generally horizontal longitudinal axis and an upper portion with a steam outlet, downcomer baflles projecting above the center of said shell and extending generally the length of and parallel to and spaced inwardly of either side of said shell for the circulation of the boiler water downwardly between each downcomer and adjacent side of the shell, fire tubes within said shell and including a generally cylindrical relatively large diameter main fire tube and thereabout a plurality of relatively small diameter return fire tubes in communication with the main fire tube for circulating hot gas to heat the boiler water, said tubes extending lengthwise longitudinally of said shell,

outlet 25, water flows downwardly between the longitudinal axis of said main fire tube being substantially directly below the longitudinal axis of said shell and said return fire tubes being positioned between said main fire tube and said downcomersto provide substantially effective increasing open area from the lower to the upper return fire tubes for accommodating the expanding volume of steam and boiler water as the mixture rises in the boiler, thereby effectively eliminating choking of the rising mixture and interface steam pockets and resultant possible formation of scale and corrosion on the tubes, and a deflector bafile extending generally the length of the upper portion of the shell and higher than said downcomers between the steam outlet and the fire tubes and to be substantially at the water level in the shell to direct the upwardly moving steam-water mixture outwardly toward the shell with the steam separating from the water, whereby the resultant momentum of the water in addition to the difference in density between the water and steam-water mixture about the fire tubes causes the water to circulate downwardly between the downcomers and shell for recirculation about the fire tubes.

2. A boiler comprising a boiler shell for boiler water and steam, said shell having an upper portion with a steam outlet, downcomer bafiles projecting above the center of said shell and extending generally the length of and parallel to and spaced inwardly of either side of said shell for the circulation of the boiler Water downwardly between each downcomer and adjacent side of the shell, fire tubes within said shell for circulating hot gas to heat momentum of the water causes the water to circulate downwardly between the downcomers and shell for recirculation about the fire tubes.

3. A boiler comprising a generally cylindrical boiler 5 shell for holding boiler water and steam, said shell having a generally horizontal longitudinal axis and an upper portion with a steam outlet, down-comer bafiles projecting above the center of said shell and extending generally the length of and parallel to and spaced inwardly of either side of said shell for the circulation of the boiler water downwardly between each downcomer and adjacent side of the shell, fire tubes within said shell for circulating hot gas to heat the boiler water, and a deflector wardly between the downcomers and shell for recirculation about the fire tubes.

References Cited by the Examiner UNITED STATES PATENTS the boiler water, and a deflector extending generally the length of the shell above said dowucomers between the steam outlet and the fire tubes and substantially at the water level in the shell to direct the upwardly moving water outwardly toward the shell whereby the resultant 2,105,801 1/1938 Watts 122-449 2,499 ,302 2/1950 Emhardt 122409 X FOREIGN PATENTS 933,496 8/ 1963 Great Britain.

KENNETH W. SPRAGUE, Primary Examiner. 

3. A BOILER COMPRISING A GENERALLY CYLINDRICAL BOILER SHELL FOR HOLDING BOILER WATER AND STEAM, SAID SHELL HAVING A GENERALLY HORIZONTAL LONGITUDINAL AXIS AND AN UPPER PORTION WITH A STEAM OUTLET, DOWNCOMER BAFFLES PROJECTING ABOVE THE CENTER OF SAID SHELL AND EXTENDING GENERALLY THE LENGTH OF AND PARALLEL TO AND SPACED INWARDLY OF EITHER SIDE OF SAID SHELL FOR THE CIRCULATION OF THE BOILER WATER DOWNWARDLY BETWEEN EACH DOWNCOMER AND ADJACENT SIDE OF THE SHELL, FIRE TUBES WITHIN SAID SHELL FOR CIRCULATING HOT GAS TO HEAT THE BOILER WATER, AND A DEFLECTOR BAFFLE EXTENDING GENERALLY THE LENGTH OF THE UPPER PORTION OF THE SHELL AND HIGHER THAN SAID DOWNCOMERS BETWEEN THE STEAM OUTLET AND THE FIRE TUBES TO DIRECT THE UPWARDLY MOVING STEAM-WATER MIXTURE OUTWARDLY TOWARD THE SHELL WITH THE STEAM SEPARATING FROM THE WATER, WHEREBY THE RESULTANT MOMENTUM OF THE WATER IN ADDITION TO THE DIFFERENCE IN DENSITY BETWEEN THE STEAM-WATER MIXTURE AND THE WATER CAUSES THE WATER TO CIRCULATE DOWNWARDLY BETWEEN THE DOWNCOMERS AND SHELL FOR RECIRCULATION ABOUT THE FIRE TUBES. 